This plant is grown directly in a block of tufa, a natural stone with a high aeration factor. Tiny root hairs are able to penetrate tufa and derive nutrition from the stone. Tufa can be regarded as being a well-aerated clay, which doesn't compact and lose its porosity, which makes for healthier plants. With the rock, the crown of the plant is held above ground level and this prevents rot on the plant as well. Roots are also less disturbed during transplanting.